CSC/ECE 517 Spring 2015/ch1a 14 RI

Thread Safety

A multi-threaded program presents the risk of race conditions, which are situations in which multiple threads rely on the same system state. This is a dangerous situation because if multiple threads access the same state simultaneously, the state could become corrupted. Thread safety avoids race conditions by guaranteeing that multiple threads can run safely, concurrently.

Background

A thread is a small set of instructions that can be handled independently by the scheduler. Multithreading is the concept of allowing multiple threads within the execution of a single process, which allows those threads to share resources. Multithreading is a useful and powerful construct within web-server environments, such as rails. For example, multiple threads could be used to handle requests from multiple users simultaneously, while also handling long running tasks in the background. As a result of multithreading, users have a better experience, because tasks that would pause execution in a single threaded application, can be allotted their own thread, and the user is never interrupted. Although having multiple threads is powerful, it is equally dangerous, due to race conditions. Race conditions occur when multiple threads are accessing the same state, most specifically the same data, and thus the output depends on the correct order of operations, but the threads execute out of order, causing the data to be corrupted.

Sources

http://www.sitepoint.com/config-threadsafe/

http://en.wikipedia.org/wiki/Thread_(computing)

http://en.wikipedia.org/wiki/Race_condition

http://en.wikipedia.org/wiki/Thread_safety